R-spondin protein is an agonist of the classic Wnt/β-catenin signaling pathway. R-spondin gene family members (RSPO) are recently found to be fused with other gene partners in some colorectal cancers (Seshagiri et al, Nature 2012 488(7413): 660-664). It is reported that a EIF3E (exon 1)-RSPO2 (exon 2) fusion gene formed by the fusion of RSPO2 gene and EIF3E gene occurs in 2% of the cancer samples in the patients having colon cancer, while a PTPRK (exon 1)-RSPO3 (exon 2) fusion gene formed by the fusion of RSPO3 gene and PTPRK gene occurs in 8% of the samples. Gene fusion events usually activate expression of R-spondins, which in turn activates Wnt signaling.
Therefore, identification of gene partners for RSPO2 fusion in cancer cell signaling pathway will provide potential opportunities for therapeutic intervention of cancers.